Z4

Z4

The Z4 is was one of the world's first commercial digital computers, designed by German engineer Konrad Zuse and built by his company Zuse Apparatebau between 1942 and 1945. The Z4 was Zuse's final target for the Z3 design, and like it, was an electromechanical, not an electronic machine. The Z4 was very similar to the Z3 in its design but was significantly enhanced in a number of respects. In 1944 Zuse was working on the Z4 with around two dozen people, including several women. Some engineers who worked at a telecommunications facility also worked for Zuse as a secondary occupation. To prevent it from falling into the hands of the Soviets, the Z4 was evacuated from Berlin in February 1945 and transported to Göttingen. The Z4 was completed in Göttingen in a facility of the Aerodynamische Versuchsanstalt (AVA, Aerodynamic Research Institute), which was headed by Albert Betz. But when it was presented to scientists of the AVA the roar of the approaching front could already be heard, so the computer was transported with a truck of the Wehrmacht to Hinterstein in Bad Hindelang, where Konrad Zuse is said to have met Wernher von Braun. In 1949 the Swiss mathematician Eduard Stiefel, after coming back from a stay in the USA where he inspected American computers, visited Zuse and the Z4. When he formulated a differential equation for Zuse, who immediately programmed the Z4 to solve it, Stiefel decided to acquire the computer for his institution in Switzerland, the Swiss Federal Institute of Technology Zurich (ETH Zurich). It was delivered to ETH Zurich in September 1950. The Z4 was also used for calculations for work on the Grande Dixence Dam. In 1950/1951 the Z4 was the only working digital computer in continental Europe, and the second digital computer in the world to be sold, beating the Ferranti Mark 1 by five months and the UNIVAC I by ten months, but in turn being beaten by the BINAC (although that never worked at the customer's site). In 1954, the Z4 was transferred to the Institut Franco-Allemand des Recherches de St. Louis (Franco-German Institute of Research) in France, where it was in use until 1959. Today, the Z4 is on display in the Deutsches Museum in Munich.

Supplement: Compared with the Z3 the memory of the Z4 consisted of 32 bit rather than 22 bitfloating point words. A special unit called the Planfertigungsteil (program construction unit), which punched the program tapes made programming and correcting programs for the machine much easier by the use of symbolic operations and memory cells. Numbers were entered and output as decimal floating point even though the internal working was in binary. The machine had a large repertoire of instructions including square root, MAX, MIN and sign. Conditional tests included tests for infinity. When delivered to ETH Zurich the machine had a conditional branch facility added and could print on a Mercedes typewriter. There were two program tapes where the second could be used to hold a subroutine (originally six were planned).